Support is requested to continue what has proven to be a highly successful program for the training of predoctoral students at the interface of chemistry and biology. Over the past ten years, this CBI training program has supported 52 graduate students, six of which have subsequently received NSF, Keck Foundation, National Defense Science and Engineering Graduate (NDSEG) or American Heart Association predoctoral fellowships. In addition, Yale has made a conscious effort to increase its representation in this interdisciplinary area through new hires and promotions at the junior and senior levels in the departments of Molecular, Cellular and Developmental Biology (MCDB), Chemistry, and Molecular Biophysics and Biochemistry (MB&B). Moreover, Yale University's recent acquisition of the former Bayer Pharmaceuticals R&D site in neighboring West Haven has allowed the launch a new Chemical Biology Institute, which will house 10 additional faculty working at the chemistry/biology interface. Given this expansion of faculty, additional funds are requested to support a total of 18 CBI predoctoral trainees. All trainees admitted to the program have at least a Bachelor's degree in a relevant field and enter via application to the Chemistry department or to the Yale Biological and Biomedical Sciences (BBS) program. Regardless of mode of entry all trainees share a common first year experience involving interdisciplinary course work, laboratory rotations, as well as close supervision and guidance from the Director of Graduate Students in conjunction with the Executive Committee. At the end of their first year, trainees chose a thesis advisor from among the 34 CBI trainers and begin intensive research with additional courses in their second year. All students teach for at least one year to aid in their training as teacher-scholars. Programs for increasing the number of minority trainees and for providing education in ethical issues related to research represent important parts of this training program. Special features of the training program include interdepartmental course work, including specially designed courses for the new trainees, a rigorous interdepartmental rotation schedule during which the trainee will experience science in three laboratories at Yale, a monthly in-house seminar program for discussion of recent results and a highly successful annual Chemical Biology Symposium with a CBI Trainee Poster competition. A new industrial rotation at Bristol Myers Squibb is now available to trainees. .